- Epidemiology
- Common in younger patients (the first episode is rare after 40 years of age)
- Mechanism (vasovagal response): trigger activates vagus nerve → ↑ parasympathetic nervous tone → ↓ heart rate, blood pressure, and cardiac contractility, ↑ peripheral vasodilation
- Clinical features
- Prodrome (eg, warmth, pallor, nausea, diaphoresis)
- Commonly followed by fatigue
- Possible triggers
- Prolonged standing
- Emotional stress, e.g., fear, the sight of blood, medical procedures
- Syncopal attacks provoked by light stimulation of the external auditory canal.
- The vagus nerve provides cutaneous sensation to the posterior external auditory canal via its small auricular branch. Sensation to the rest of the canal is from the mandibular division of the trigeminal nerve